where \(\eta _0 = 10^{13}\)  Pa s is the melting point viscosity [1]} and T\(_{melt}\)  is the melting point. A critical Rayleigh number of 1000 was used for the onset of convection following [1]}. However this critical value can be as low as 40 [3]} in a porous medium. In our simulations these Ra values have not been reached at T \(\lesssim \)  T\(_{melt}\) .
